1css定位

    <style>
        .wrap {
            position: relative;
            background: #333;
            height: 300px;
            width: 300px;
        }
        .box {
            position: absolute;
            top: 50%;
            left: 50%;
            background: #999;
            width: 100px;
            height: 100px;
            margin: -50px 0 0 -50px;
        }
    </style>
</head>
<body>
    <div class="wrap">
        <div class="box">
        </div>
    </div>
</body>

image.png

适用于父容器和子容器的宽高是确定的。

2.transition

    <style>
        .wrap {
            position: relative;
            background: #333;
            height: 300px;
            width: 300px;
        }
        .box {
            position: absolute;
            top: 50%;
            left: 50%;
            background: #999;
            width: 100px;
            height: 100px;
            transform: translate(-50%, -50%)
        }
    </style>
</head>
<body>
    <div class="wrap">
        <div class="box">
        </div>
    </div>
</body>

image.png

利用c3的动画属性

3.强大的flex

    <style>
        .wrap {
            position: relative;
            background: #333;
            height: 300px;
            width: 300px;
            display: flex;
            justify-content: center;
            align-items: center;
        }
        .box {
            background: #999;
            width: 100px;
            height: 100px;
        }
    </style>
</head>
<body>
    <div class="wrap">
        <div class="box">
        </div>
    </div>
</body>

image.png

定义父容器为flex容器，添加设置主轴和次主轴居中 justify-content: center; align-items: center;代码简洁优雅

4.设置table的属性，模拟表格定位

    <style>
        .table {
            display: table;
            height: 300px;
            background: #aaa;
        }

        .cell {
            display: table-cell;
            width: 300px;
            background: #999;
            vertical-align: middle;
            text-align: center;
        }
        .img {
            width: 100px;
            height: 100px;
            background: #333;
            display: inline-block;
        }
    </style>
</head>
<body>
    <div class="table">
        <div class="cell">
            <div class="img">
            </div>
        </div>
    </div>
</body>

页面看成一个表格的思想，也很不错

用table完成一个两边固定，中间自适应(图片居中)的经典布局：

  <style>
        .table {
            display: table;
            width: 100%;
            background: #aaa;
        }

        .cell {
            display: table-cell;
            /* background: #999; */
            vertical-align: middle;
            text-align: center;
        }
        .table .left,.table .right {
            width: 300px;
            height: 300px;
            background: burlywood;
        }
        .img {
            width: 100px;
            height: 100px;
            background: #333;
            display: inline-block;
        }
    </style>
</head>
<body>
    <div class="table">
        <div class="cell left"></div>
        <div class="cell">
            <div class="img">
            </div>
        </div>
        <div class="cell right"></div>
    </div>
</body>

image.png